LIPH调控乳腺癌干细胞增殖分化的作用及机制

Cancer stem cells are considered to be the root of the recurrence and metastasis of breast cancer, and their self-renewal and multi-directional differentiation properties is the critical factor to cancer recurrence.The mechanisms of how secreted protein LIPH regulates breast cancer stem cells are unknown. In the preliminary work, it was found that the serum LIPH expression was significantly higher in the breast cancer patients with recurrence and metastasis compared to the cases without, and the LIPH protein expression was significantly related to the worse prognosis in clinical breast cancer patients. The proliferation and invasive ability of MDA-MB-231 cells was enhanced after cultured with LIPH protein in vitro. Moreover, exogenous expression of LIPH protein significantly increased the breast cancer stem cells ratio, companied with the up-regulated expression of nuclear β-catennin. Therefore, we speculate that LIPH may promote the proliferation and differentiation of cancer stem cells by up-regulating the activity of Wnt/β-catennin signaling pathway through autocrine or cytoplasmic expression. In order to prove this hypothesis, we intend to study the effect and mechanism of LIPH on the proliferation and differentiation of breast cancer stem cells in vitro and mouse situ implantation model in order to provide a theoretical basis for blocking recurrence and treatment of breast cancer.

肿瘤干细胞是乳腺癌术后复发的根源，其自我更新和多向分化潜能是导致乳腺癌复发和转移的关键。分泌蛋白LIPH调控乳腺癌干细胞的作用机制未明。我们在前期工作中发现复发转移的乳腺癌血清中LIPH表达明显高于无复发转移组，且与乳腺癌的不良预后显著相关。我们用LIPH蛋白孵育乳腺癌MDA-MB-231细胞后其增殖能力显著升高。通过外源性上调MDA-MB-231细胞的LIPH蛋白表达后，乳腺癌肿瘤干细胞的比率明显上调，且干细胞分化相关重要因子β-catennin核表达显著上调。因此，我们推测LIPH可能通过自分泌或胞浆高表达双重途径上调Wnt/β-catennin信号通路活性促进肿瘤干细胞的增殖和分化。为了证明这一假设，本研究以乳腺癌肿瘤干细胞和小鼠原位种植模型为研究对象，明确LIPH对乳腺癌肿瘤干细胞的增殖和分化功能的调控作用并阐明其调控机制，为进一步通过抑制LIPH控制乳腺癌的复发提供理论依据。

脂肪酶成员H（LIPH）是甘油三酯脂肪酶家族的一个新成员，其在乳腺癌中表达的临床意义尚不清楚。在本研究中，我们研究了144例三阴性乳腺癌（TNBC）患者的LIPH与致瘤行为之间的关系，检测了LIPH敲除对CD44+/CD24-干细胞的比例和成球能力的影响，同时评估了LIPH在乳腺癌细胞迁移和侵袭中的作用。此外，用海马法测定了LIPH沉默对线粒体呼吸的影响。最后，通过串联质谱和蛋白免疫印迹检测LIPH沉默对蛋白质表达的影响。我们发现LIPH的表达与淋巴结和远处器官的转移有关（P=0.025），导致乳腺癌患者的生存率低（P=0.027）。LIPH基因敲除显著降低了CD44+/CD24-干细胞样细胞的比率及其乳腺球形成能力。LIPH沉默促进细胞凋亡，阻滞细胞周期于G2/M期，降低线粒体氧化相关耗氧率，降低代谢。LIPH抑制肿瘤细胞间粘附，促进上皮-间充质转化。串联质谱分析显示，68种蛋白在LIPH沉默细胞中差异表达，LIPH介导的肿瘤细胞粘附调节依赖于整合素相关的CAPN2和paxillin信号。总的来说，我们的发现提供了强有力的证据，证明LIPH的上调促进了TNBC细胞的转移和干细胞。因此，靶向LIPH是预防TNBC中转移的一个潜在可行策略。